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E30 M50 swap with E90 booster

04-14-2019, 08:47 PM

I am new to the forum and I am posting this as it might help those trying to get the e90 brake booster to fit with the OBD1 intake manifold. I searched alot of threads and posts on the topic but could not find any definitive info on how get it to work.

The problem i ran into is that the e90 booster with e90 master cylinder and brake fluid reservoir do not clear the throttle body and more specifically, they do not clear the throttle position sensor. I tried about 6 or 7 different reservoirs from different BMW models but none worked. So the only solution i found is to remote mount the brake fluid reservoir and connect it to the MC with hoses. I was able to find a stock 92 BMW 7 series (E32) remote mount brake fluid reservoir with two fluid outlets at a local pic a part and it worked perfectly. I also got the plastic MC fittings from the same car . As far as connection to the brake pedal, all i had to do is take the stock U-shaped e30 bracket from the booster (the one with the threaded hole at the back of it) and weld it to the U-shaped e90 booster bracket and it fit perfectly, no cutting or rethreading needed.

I also used a separate reservoir and bracket for the clutch fluid which i got from believe it or not, a saturn, see pics, and that too worked perfectly. I still had to shave down a couple of fins on the intake manifold that were almost touching the brake booster.

I hope this helps anyone trying to use an e90 booster and MC combo in their M50/S50 swap with the OBD1 manifold.

Comment

Good job. What did you do about the hardlines? bent them over to the passenger side? found a metric female M10 to male M12 adapter? There's an extensive thread on this subject somewhere in this subforum. Here's my solution...

1. 2002 reservoir fits directly with new smaller grommets. Reuses the original E30 cap and level sensor without modifying anything. No need to remote mount a reservoir or use a separate clutch reservoir.

2. I used M10 to M12 line adapters with custom hard lines and a Metric T to make it plug and play. No need to bend any of the hardlines and reflare on the car. 100% reversible.

3. I then bought a custom made clevis which makes it plug and play. I had a couple of bad E90 boosters leak internally. If you modify the booster, you will have to do it each time you change it.

Comment

Thank you. Yes, for the steel brake lines, i just bent them to the other side of the MC and connected them using an M10 to M12 brass bubble flare adapter i got from summit racing. I do like your solution better with 2002 reservoir. I could not find any 2002 reservoirs at any pic a part locally (Las Vegas), very rare, so i had to resort to the e34 remote reservoir. As far as the clevis, i have a couple of spares in case i ever have to replace the booster with another e90 one.

Comment

I had the grommets in my parts bin because they are the same ones M3 guys with CF airboxes use to relocate the reservoir. I believe they are part number 34311121911 which are 2002 grommets so you know they are the right inner diameter. Double check the dimensions and the outer diameter to be sure.

"I'd probably take the E30 M3 in this case just because I love that little car, and how tanky that inline 6 is." - thecj